摘要:

A hybrid four layer guide (FLG) including a glass guide and a 2-docosylamino-5-nitropyridine Langmuir–Blodgett film is described, and some tests are reported on an electro-optic modulator based on this FLG. The modulation of laser diode light was obtained by guided mode interference, without a Mach–Zehnder configuration of the device. From the modulated signal ther22electro-optic coefficient was calculated as 11 pm/V. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120921

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Strained single-quantum-well, broadened-waveguide GaInAsSb/AlGaAsSb diode lasers have exhibited room-temperature threshold current densities as low as50 A/cm2,one of the lowest values reported for diode lasers at room temperature. These lasers, grown by molecular beam epitaxy, have emission wavelengths of∼2.05 &mgr;m,characteristic temperature of 65 K, internal quantum efficiency of 95&percent;, and internal loss coefficient of7 cm−1.Single-ended cw power of 1 W is obtained for a 100-&mgr;m aperture. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.120922

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Experimental results on self-diffraction of periodically phase-modulated laser beams from a relief grating formed on a free surface of a cubic photorefractiveBi12TiO20crystal due to the piezoelectric effect are reported. Periodic intensity modulations of the reflected beams up to10−2due to energy exchange at this unshifted phase grating are measured. The modulation depends linearly on the fringe spacing and on the amplitude of an externally applied electric dc field. The observed self-diffraction process is independent of the light polarization. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120923

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Optical absorption and multiphonon relaxation have been investigated forNd3+-dopedZnCl2-based glass. The intensity parameters for radiative transitions ofNd3+were determined to be&OHgr;2=4.97×10−20 cm2,&OHgr;4=7.39×10−20 cm2and&OHgr;6=5.12×10−20 cm2.All of the&OHgr;tparameters, especially&OHgr;4,ofNd3+in theZnCl2-based glass were large compared with those reported for oxide and fluoride glasses. Multiphonon relaxation rates for three emission levels ofNd3+were determined from lifetime measurements. The multiphonon relaxation rates in theZnCl2-based glass were extremely low, because of the low-phonon-energy of the matrix. Values were found to obey the energy-gap law in the same manner as the values inEr3+-dopedZnCl2-based glasses. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120924

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the use of a low concentration polymer network to stabilize electric field-induced diffraction gratings in cholesteric liquid crystals. The stabilized gratings can be electrically switched between a zero-field “on” state, which exhibits approximately 75&percent; diffraction efficiency, and a moderate field (typically 3 V/&mgr;m) “off” state. Grating spacings between 1.7 and 30 &mgr;m are obtained in a 10 &mgr;m thick cell by variation of the concentration of chiral dopant used to form the cholesteric liquid crystal. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120925

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An increase of the relative intensity noise of nearly single-mode distributed feedback lasers with respect to that predicted by single-mode theory after propagation in dispersive fiber at frequencies up to 5 Ghz has been measured. A simplified multimode theory is presented which explains the increase in noise. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120926

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A complete theoretical approach to the electromagnetic properties of vertical-cavity surface-emitting lasers (VCSELs) is presented. The solution of the 3D vector Maxwell equations is obtained by means of a generalized vectorial transform matrix. Results for the characterization of laser modes include modal frequencies, cavity losses, and eigenmode light-field vector patterns. As an example, modal properties of air-post index-guided VCSELs are analyzed for various cavity design parameters. Scattering losses due to modal mismatch at cavity interfaces are found to be small and, hence, would not overcompensate potential cavity design improvements based on increased relative index steps. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120927

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A nonmechanical method for fabricating a metallic narrow constriction between two electrodes using electrochemical deposition is described. The width of the constriction can be adjusted by slowly dissolving metal atoms away or redepositing atoms onto the constriction which can be controlled flexibly by the electrodes’ potentials. Well-defined plateaus near the integer numbers of the conductance quantum have been observed in these constrictions at room temperature. Since no mechanical movements are involved, this method has the potential of fabricating nanoconstrictions with long term stability. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120928

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Raman scattering has been used to probe short-range structural information on lanthanum-doped lead titanate ceramics(LaxPb1−xTiO3)forx,ranging from 0.0 to 0.30. In highly doped samples(x>0.27),x-ray diffraction measurements indicate a cubic structure, although measurements of Raman scattering at temperatures above and below the tetragonal to cubic transition showed a residual short-range structural disorder in the cubic phase. Moreover, for these highly lanthanum-doped samples, a well-defined temperature-induced ferro–paraelectric phase transition disappears, which suggests a relationship between local disorder and relaxor behavior in this material. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120929

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A multichannel spectroscopic ellipsometer based on the rotating-compensator principle has been applied to obtain the evolution of spectra (1.5–4.0 eV) in the normalized Stokes vector of the light beam reflected from the surface of a nanocrystalline diamond film during growth. Spectra in the ellipsometry angles (&psgr;, &Dgr;) provide the time evolution of the microstructure and optical properties of the film in thin layers, whereas the spectra in the degree of polarization provide the time evolution of nonuniformities in the growth process attributed to light scattering by diamond nuclei in the initial stage of growth and to thickness gradients over the probed area in thicker layers. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120930

出版商:AIP    

年代:1998

数据来源: AIP